1. Field of the Invention
The present invention relates to an electromagnetic reciprocating compressor, and more ii particularly to a compact electromagnetic reciprocating compressor with a high volume fluid discharge capacity.
2. Description of the Related Art
A conventional electromagnetic reciprocating compressor is provided with a piston having an integrally formed armature, a fixed electromagnet provided around the armature, and a spring for urging the piston in one direction, and driven by a half-wave-rectified alternating current. In operation, when the fixed electromagnet is excited by a half-wave electric current, the piston is moved by the electromagnetic effect of the armature and the electromagnet in a direction compressing the spring. Then, with a next half wave, the fixed magnet is demagnetized, and the piston is pushed back to return to its original position by the rebound effect of the spring. With the reciprocation of the piston in a compression chamber as described above, a fluid such as air is sucked into the compression chamber, compressed and discharged. In this type of compressor, the quantity of fluid discharged is determined by the dimensions of the compression chamber and the operation frequency the piston operates at.
When obtaining a larger discharge quantity by this type of compressor, coupling a plurality of compressors may be considered. For example, in the electromagnetic compressor disclosed in Jpn. Pat Appln. KOKAI publication No. 61-207883, a plurality of compressors are integrally coupled in a linear or radial form, and respective fluid passages of a plurality of compressors are connected in parallel, thereby increasing the discharge quantity.
The above-described electromagnetic reciprocating compressor has the following disadvantages. The discharge quantity can be increased by integrally coupling a plurality of compressors. However, this leads to an increase in overall size. For example, assuming that a compressor with a large discharge quantity in which a plurality of compressors are integrally incorporated is used as an outdoor blower, a drip-proof housing must be provided. In such a case, since the entire apparatus including the housing is increased in size and the installation place is restricted in particular, a reduction in size is demanded. Further, there is a disadvantage in the complicated connections needed. For example, much wirings must be gathered by using connectors in order to provide the electrical wiring between a plurality of compressors.
Furthermore, in order to prevent pulsation of a fluid discharged from the compressor from being transmitted to the outside, there is required an air tank for buffering, which temporarily accumulates the fluid discharged from the compressor. When a plurality of compressors are coupled to discharge a large quantity of fluid, the pulsation becomes prominent, and the air tank must have a large capacity in order to suppress this pulsation, which results in a further increase in size.
In order to eliminate the above-described problems, it is an object of the present invention to provide a compact electromagnetic reciprocating compressor with a large discharge quantity which has a plurality of compression portions.
To achieve this aim, according to the present invention, there is provided an electromagnetic reciprocating compressor comprising: a casing; and a plurality of fluid compression portions which are arranged in the casing, each of which has a piston, and which are arranged in such a manner that these pistons move along directions parallel to each other. Each of these compression portions includes: a cylinder for accommodating therein the piston so as to be capable of reciprocating; a compression chamber defined by the piston for compressing a fluid in the cylinder; a spring for urging the piston in a direction for compressing the fluid in the compression chamber, one field core having a pair of opposed portions for forming magnetic poles oppositely-arranged along a diametral direction of the piston, a coil which is wound around the field core and moves the piston against the urging force of the spring when excited, and a discharge chamber for receiving the compressed fluid from the compression chamber when the coil is demagnetized. Moreover, the compressor comprises passaging means which are provided in the casing and communicates discharge chambers of the respective compression portions, the field core of each compression portion being integrally formed so as to commonly use a boundary portion with a field core of an adjacent compression portion, and a power supply device for supplying a half wave of an alternating electric current to the coil in such a manner that an excitation direction of at least one of a plurality of the field cores can be opposed to those of other field cores.
According to this compressor, the piston is moved in one direction by the electromagnetic effect of an armature and the coil for exciting the field core, and moved in an opposed direction by the spring means when the coils are demagnetized. The fluid is compressed/discharged in the compression chamber by the operation of this piston. Respective pistons of a plurality of the compression portions are arranged so as to be parallel to each other, and the field core is excited to drive each piston when an alternating half wave is supplied. Since the electric circuit means supplies an alternating electric current in such a manner that some of a plurality of field cores are excited in a direction opposed from those of other field cores, the pistons of some of a plurality of compression portions are moved in directions opposed to each other. Therefore, the vibrations generated cancel each other out, dissimilar to the case where the pistons simultaneously reciprocate, and the vibrations of the compressor are suppressed.
In addition, the boundary portion of the field cores can be commonly used by the adjacent compression portions. Additionally, the discharge chambers communicate with each other by the passage means, and the discharge chamber of the compression portion which is not in the discharge stroke is utilized as the compression chamber of the compression portion which is in the discharge stroke. Thus, the capacity of the discharge chamber is substantially increased, thereby reducing the pulsation.
Further, according to another aspect of the present invention, there is provided a blower which includes an electromagnetic reciprocating compressor in a housing. This compressor comprises: a casing; and a plurality of fluid compression portions which are arranged in the casing, each of which has a piston and which are arranged so that the pistons can move along directions parallel to each other, each of these compression portions having: a cylinder for accommodating therein the piston so as to be capable of reciprocating; a piston for defining a compression chamber for compressing a fluid; a spring for urging the piston in a direction for compressing the fluid in this compression chamber; one field core having a pair of opposed portions forming magnetic poles oppositely-arranged along the diametrical direction of the piston; a coil which is wound around the field core and moves the piston against the urging force of the spring when excited; and a discharge chamber for receiving the compressed fluid from the compression chamber when this coil is demagnetized. Furthermore, in this compressor, the field core of each compression portion is integrally-formed so as to be capable of commonly using a boundary portion with a field core of an adjacent compression portion. Moreover, the compressor comprises: a power supply for supplying a half wave of an alternating electric current to the coil in such a manner that at least one of a plurality of field cores has an excitation direction opposed from those of other field cores; and a head cover which covers the cylinder and is attached to the casing, defining the compression chamber in the cylinder with the piston, defines the discharge chamber having an air-tight structure at the outside of the each cylinder, and has a passage communicating the discharge chambers with each other and a nozzle protruding toward the outside and communicating the discharge chambers with the outside. In addition, the blower includes: a tank arranged in the housing; and a bush which is formed in the tank and accommodates the nozzle in the sealed state, and receives the fluid compressed in each compression chamber into the tank.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.